1. Field of Invention
The present invention relates to liquid crystal display devices and electronic apparatuses. More specifically, the invention relates to a construction of a transflective liquid crystal display device capable of performing display with sufficient brightness, in particular, even in a transmission mode.
2. Description of Related Art
A transflective liquid crystal display device which performs a display both in a reflective display mode and a transmissive display mode, can perform a clear display even in dark surroundings while reducing the power consumption by switching its display mode between the reflection mode and the transmission mode depending on the ambient brightness.
There has been proposed a transflective liquid crystal display device in which a liquid crystal layer is interposed between light transmissive upper and lower substrates, and a reflection film, which is made of a metal film such as aluminum and has light transmissive slits formed therein, is provided on the inner surface of the lower substrate, the reflection film functioning as a transflective reflection film. In this case, in the reflection mode, after external light incident from the upper substrate side passes through the liquid crystal layer, the light is reflected by the reflection film arranged on the inner surface of the lower substrate, and then the light passes through the liquid crystal layer again to be provided for display from the upper substrate side. On the other hand, in the transmission mode, after light from a backlight, which enters from the lower substrate side, passes through the liquid crystal layer via the slits formed in the reflection film, it can be provided from the upper substrate side for display. Accordingly, in the reflection film, the region where the slits are formed constitutes the transmissive display region, and the region where the slits are not formed constitutes the reflective display region.
Such a transflective liquid crystal display device performs a display, for example, in such a way that, when the thickness of the liquid crystal layer is constant, light passes through the liquid crystal layer twice in the reflective display region, but light passes through the liquid crystal layer only once in the transmissive display region.
In this way, in the reflective display region and the transmissive display region, the number of times that light passes through the liquid crystal layer is different from each other. However, the alignment control of liquid crystal molecules in the liquid crystal layer is carried out by applying an electric field to the liquid crystal in the same pixel so that it is difficult to obtain a high contrast display in both the transmissive display region and the reflective display region whose display manners are different from each other. For example, a conventional transflective liquid crystal display device has a problem that, when optimizing the luminance in the reflection mode, luminance in the transmission mode is insufficient.
Thus, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 11-242226, there is proposed a transflective liquid crystal display device in which the thickness of a liquid crystal layer in a reflective display region and the thickness of the liquid crystal layer in a transmissive display region, in one dot region, are constructed differently to correct the length of optical path for every display mode, and thus to obtain a high bright display even in the transmissive display. FIG. 5 illustrates a cross-sectional structure of one dot region in a liquid crystal display device with the corresponding construction. A liquid crystal display device 100 shown in FIG. 5 includes a liquid crystal panel 101 and a backlight 160 arranged on the backside thereof. The liquid crystal panel 101 is constructed by interposing a liquid crystal layer between the upper substrate 120 and the lower substrate 110. The lower substrate 110 includes a transparent substrate 110A, a resin layer 112 partially formed on the substrate 110A at the liquid crystal layer side, a reflection layer 111 partially formed on the resin layer 112, a pixel electrode 113 covering the dot region in the drawing, and a polarizing plate 116 arranged on the outer surface of the substrate 11A. The upper substrate 120 includes a transparent substrate 120A, a counter electrode 123 formed on the substrate 120A at the liquid crystal layer side, and a polarizing plate 126 formed on the outer surface of the substrate 120A.
Also, the region of the lower substrate 120 in which the reflection layer 111 is formed constitutes the reflective display region 130, and in the dot region not including the reflective display region 130, the region where the pixel electrode 113 is formed constitutes the transmissive display region 140.